JPS62216624A - Permselective composite membrane for separating gas - Google Patents

Abstract

PURPOSE:To obtain a composite membrane for separating gas excellent in performance by allowing polyorganosiloxane wherein the end of a side chain is subjected to amino denaturation to react with polyorganosiloxane wherein the end of the side chain is subjected to isocyanate denaturation on a fine porous supporting membrane. CONSTITUTION:Polyorganosiloxane, shown in formula I, wherein the end of a side chain is subjected to amino denaturation and polyorganosiloxane, shown in formula II, wherein the end of the side chain is subjected to isocyanate denaturation are allowed to react with each other on a fine porous supporting membrane having 10-5,000Angstrom hole size of the surface. As a reaction method, the following method is adopted wherein a denature siloxane soln. having 0.01-1wt% concn. is coated on the fine porous supporting membrane and thereafter recoated at 50-200 deg.C and dried for 0.5-110sec. When a mixing ratio of the amino denatured substance of denatured siloxane and an isocyanate denatured substance is regulated to (25:75)-(75:25) by pts.wt., formability of a membrane is made favorable.

Description

Detailed Description of the Invention 3. 37411 Description of the Invention 1 Industrial Application Field The present invention relates to a permselective composite membrane for gas separation having good gas permeability. More specifically, it relates to a separation membrane that is effective for separating oxygen-enriched air by 1.7% from air.

[Prior Art] Currently, devices that utilize combustion energy, such as home heating appliances, automobile engines, boilers, etc., are operated on air with an oxygen concentration of approximately 20%. There is. Now, if oxygen-enriched air with enhanced odor is used in these devices, it is possible to not only increase the combustion efficiency but also to significantly raise the combustion temperature.

Now, as a method for obtaining such oxygen-enriched air, a membrane separation method is known in which a pressure difference is created before and after a gas separation membrane and the driving force is used to condense oxygen in the atmosphere. In this membrane separation method, the cost of the oxygen-enriched air obtained is determined by the selectivity and permeability of the gas separation membrane, which requires the development of gas separation membranes with high selectivity and high permeability. has been done.

Conventionally, as such a gas separation membrane, on a porous support membrane,
Polysiloxane containing 1 to 50 amino groups per 1,000 siloxanes is bonded to a polyfunctional compound containing at least one functional group that reacts with an amino group! Nijime crosslinked composite membrane (JP-A-59-12020
7> or a selectively permeable membrane obtained by the reaction of a polyisocyanate component having an isocyanate group in a side chain with a polyamine component (JP-A-59-209609>) is known.

[Problems to be solved by the invention] However, the above 1. +lBunsho 59120207 and Japanese Patent Publication No. 59120207
9-209609 is particularly important because if you try to make a selective composite membrane for gas separation with high permeability by thinning the thickness of the silicone layer, which is the main component of the thin film layer, pinholes will occur and the selectivity will decrease. However, it was not possible to create a selective composite membrane for gas separation that had both sufficiently high permeability and selectivity.

The present invention aims to solve these problems and provide a selective composite membrane for gas separation that has sufficiently high permeability and selectivity.

[Means for Solving Problem 1] The present invention involves reacting a polyorganosiloxane whose side chain ends are modified with an amine and an organosiloxane whose side chain ends are modified with an isocyanate on a microporous support membrane. It is characterized by a permselective composite membrane for gas separation in which a thin film is formed.

The polyorganosiloxane in which the end of the side chain of the present invention is amino-modified is a polymer having an amine group at the end of a part of the side chain of a polyorganosiloxane having a repeating unit of a siloxane bond in the main chain. The following polymers may be mentioned.

R2<CI-b) O H N](2 (In the formula, R1 and R2 are lower alkyl groups such as methyl, ethyl, and propyl groups, or derivatives thereof, or phenyl groups, or derivatives thereof, and R3 is methyl. basis,
A lower alkyl group such as an ethyl group or a propyl group, or its XS form, P and P' are integers from 2 to 10, and n0m is 10
Preferred embodiments will be described below using integers from 0 to 2000.

R1 and R2 in structural formula (I) are the same or different, and are lower alkyl groups such as methyl group, ethyl group, and propyl group,
or a derivative thereof, or a phenyl group, or a derivative thereof. Among these, methyl group is particularly preferred since it has the best film-forming properties. R3 is a lower alkyl group such as a methyl group, an ethyl group, a propyl group, or a derivative thereof 1, P and P' in structural formula (1) are integers from 2 to 10, but when P and P' are 1 If it is less than 11 or more than 11, the reactivity of the amino group with the isocyanate-1 group is unfavorable. n0m is 100 or more and 2000 or less. "]
If 10 m is less than 100 m, the film forming property will be poor,
This is not preferable because the thin film on the microporous support will have many pinholes. If n0m exceeds 2000, GJ1
This is not preferable because the solubility of this amine-modified siloxylin in the solvent l\ becomes poor and it is difficult to form a thin film. If the pin is less than 0.2, the reactivity with the isocyanate-modified siloxane is low, and if the plenum on the crotch of the microporous support exceeds 0.2, the gel This is not preferable because it becomes a chemical compound and cannot be formed into a thin film.

In the present invention, the polyorganosiloxane whose side chain terminals are modified with isocyanate is a polyorganosiloxane having a repeating unit of a quinane bond in its main chain, and which has isocyanate groups at the terminals of some of its side chains. For example, the following combination of hands can be mentioned.

GO (However, R4 and R5 are lower alkyl groups such as methyl group, ethyl group, and propyl group, or 4 is a derivative thereof, or phenyl group, or its NA 2S form, and R6 is a methyl group, ethyl group, propyl group, etc.) or a derivative thereof, R7 is 1-401'' (CHb+TSCNX (q, a' is an integer of 2 to 10, X is a carbon number of 2 to 16
The right side of is l), n'' is an integer from 100 to 2000, and preferred embodiments are described below.

@R4 and Rs in formula (II) are the same or different,
It is a lower alkyl group such as methane, ethyl group, propyl group, or a derivative thereof, or phenyl group, or a derivative thereof. Among these, methyl group is preferred because it has the best film-forming properties. R6 is a methyl group, an ethyl group,
It is a lower alkyl group such as propyl yuzu, or a derivative thereof.

Q and Q' in R7 must be integers from 2 to 10, but q
.

If q is less than 1 or greater than 11, the reactivity of the isocyanate base and the amine base of the amino-modified siloxylin will be low, which is not preferred.

× indicates that the organic component having 2 to 16 carbon atoms is an aliphatic alkylene group having 2 to 15 carbon atoms, an aliphatic group having 5 to 16 carbon atoms, or an aromatic group having 6 to 16 carbon atoms. Specific examples of such 41 bases include i-lylene group, methylene diphenyl group, oxydiphenyl group, 1-namebulene group, naphthyl group, gysilylene group, cyclohexyl group, etc. n"+rn" is an integer from 100 to 2000, and n-+m
- becomes 100), the film forming property becomes poor,
A thin film formed on a microporous support film is not preferable because it will have many pinholes. When n-+m- exceeds 2,000, the solubility of the isocyane I/modified silyl] in the solvent becomes poor, making it difficult to form a thin film, and the value is 0.2 or less. If the ratio is less than 0.001, the reactivity with the amino-modified syrogylene of structural formula (1) will be low and the thin film on the microporous support will have many pinholes. Therefore, it is undesirable.

It is not preferable because it is highly reactive with sun and forms a gel-like substance, making it difficult to form a thin film.

The microporous support membrane used in the present invention does not provide gas permeation resistance by itself, but has the function of supporting the membrane obtained by reacting amino-modified siloxane and isocyanate-modified siloxane. The size of the pores on the surface is about 10 to 5000, preferably about 10 to 1000.
It's a person. Further, it is preferable to have an asymmetric structure that does not easily cause gas permeation resistance. As for gas permeability, the nitrogen permeation rate is 10 (m'/Tl12-hr-a
tm) or more are preferred. Examples of such microporous support membranes include porous glass materials, sintered metals, ceramics, cellulose Nisdell asymmetric membranes, polyethersulfone asymmetric membranes, polysulfone asymmetric membranes, polyimide asymmetric membranes, and the like. Among these, polysulfone asymmetric membranes are preferred because they have sufficient gas permeability and appropriate pore sizes.

The thickness of the thin film obtained by reacting amino-modified siloxane and isocyanate-modified siloxane on a microporous support film is:
A thinner membrane is preferable because it can increase gas permeability, but a thinner membrane causes pinballing and reduces the selectivity of the composite membrane. In the present invention, it has become possible to reduce the thickness of the pinhole-free thin film to about 0.1 μm. If it is made thinner than that, pinholes will occur, which will reduce the selectivity of the composite membrane, which is not preferable.

Next, a method for producing a selectively permeable composite membrane for gas separation according to the present invention will be explained.

The amino modified compound represented by formula (1) [1 Shirogyrin (a,
Although it can be produced by the following method, it goes without saying that the amino-modified silica 4:stone of the present invention is not limited to that produced by this method.

For example, the following general formula R1R3 R2 (CHZ) O il (CTo).

D Nt12 (in the formula, R is an alkyl group having 1 to 4 carbon atoms, R1
, R2, R3, l), I)' is the same as defined above) by heating in the presence of water and combining them while hydrolyzing.

The isocyanone-modified siloxane represented by the formula (1) can be produced by the following method.

For example, the following general formula % formula % (1 (However, in the formula, R is an alkyl group having 1 to 4 carbon atoms, R8 is
(CH27N to I (CH2゛ and y N H
2.

OfCH2keq O! -I, (CH2→--
ys+-1 (Q, Q't are integers from 2 to 10), Z is N+
-12 base, Ol-1 group, SH group, R4, R
5, R6t is the same as defined above) is heated in the presence of water to co-metalize, and a large excess of trifunctional isocyanonate is reacted with the resulting compound.

The amino-modified siloxane and isocyanate-modified siloxane thus obtained are dissolved in a solvent to prepare a mixed solution. The solvent used at this time must be a non-poor medium that does not attack the microporous support membrane, and must be selected depending on the material of the microporous support membrane. For example, when using a polyethersulfone asymmetric membrane or a polysulfone asymmetric membrane as a microporous support membrane, cyclohexane, isopentane, ethyl ether, ;-rifml n as a solvent.
l-Lifluoroethyne, cyclohexyl, 0-power 1
Nan etc. are preferred. The depth of each modified silane is preferably 0.01 vt% or more and Qwt% or less. The mixing ratio of the amino-modified siloquiline and the isocyanate-modified siloxane is preferably from 5 parts by weight to 25 parts by weight to 25 parts by weight to 75 parts by weight, from the viewpoint of improving film forming properties. When preparing a mixed solvent,
It is preferable to dissolve the amino-modified siloxane and the isocyanate-modified siloxane separately in a solvent, or to mix the two solutions. When a concentrated solution of an amino-modified siloxane and an isocyanate-modified siloxane are brought into contact with each other, gelation occurs instantaneously due to the high reactivity, which is not preferable.

The thus prepared mixed solution of amino-modified siloxane and isocyanate-1-modified siloxane is then coated on the crotch of the microporous support. Examples include coating using a roll coater such as a slit coater, reverse coater, and gravure coater, and coating using a wink coating method after dipping, a spray coating method, and the like. At this time, if the pores of the microporous support membrane are pre-impregnated with a non-solvent of the mixed solution, such as water or ethylene glycol, the mixed solution can be prevented from soaking into the pores, and pinball-free. This is preferable because a thin film can be formed.

The coating and drying of this mixed solvent is preferably carried out at a temperature that does not cause thermal deformation of the microporous support membrane, usually from 50°C to
200"C. Also, after coating, 0°5 seconds to 110"C.
Drying for 2 seconds, preferably 0.5 seconds to 5 seconds, reduces pinholes in the resulting thin film.

In the manner described above, the permselective composite membrane for gas separation of the present invention can be obtained.

The thus obtained permselective composite membrane for gas separation of the present invention can be used for gas separation to obtain oxygen-enriched air from air, and for separating other specific gases such as carbon dioxide, hydrogen, carbon oxide, and helium. Although it can be used for general separation membranes, it is particularly preferable to use it for separating oxygen-enriched gases.

[Example] The present invention will be explained based on examples.

The method of measuring the characteristic value and the method of evaluating the effect of the present invention are as follows.

(1) Gas permeability The permselective composite membrane for gas separation of the present invention is separated, the pressure on the downstream side is set to 2 atm, and the pressure on the downstream side is set to 1 atm, and gas (oxygen or The nitrogen) permeation rate was measured using a precision membrane flowmeter 5F-101 (manufactured by Standard Technology), and the oxygen permeation rate was used as a measure for evaluating gas permeability.

(2) Gas separability The separation coefficient, which is the ratio of the oxygen permeation rate to the nitrogen permeation rate determined above, is used as a measure for evaluating gas separability.

Example 1 CHg C city CH2 (CH2) 3 H (CH2) 2 H2 (-=0.026> n +rn n0m (number average degree) = 1600] 1
0.1 wt% dissolved in trifluoroethane, C++
(CH2) 3'' H (CH2) 2 H C-〇-[4 CH+ m' n-+m- (number average precision>=12o.

The isocyanate-modified siloxane represented by is added to trichlorotrifluoroethane at 0.0%. lt% and mix these two liquids at a ratio of 1:1 to prepare a coating liquid. This coating solution was applied to the surface of a polysulfone microporous support membrane whose pores had been previously impregnated with water to a wet thickness of 25 μm, and after 2 seconds of application, it was dried with hot air at 100°C. Furthermore, the coating liquid was applied once again to a wet thickness of 20μ and dried under the same conditions. The oxygen permeation rate of the permselective composite membrane for gas separation obtained by J: is 8 (m'/m2・hr-atm
), and the oxygen/nitrogen separation was 2.1.

Examples 2 to 4 Using various amino-modified silokinanes and isocyanate-modified silokinanes shown in Table 1, a permselective composite membrane for -C gas separation was prepared in the same manner as in Example 1. The results are shown in Table 1.

As is clear from the above, the permselective composite membrane for gas separation of the present invention has both high gas permeability and selectivity.

[Effect] The present invention is a method of forming a thin film by reacting polyorganosyl, loxane whose side chain terminals are amine-modified and polyorganosyl loxane whose side chain terminals are modified with isocyanate (I) on the crotch of a microporous support. Since the selective permselective composite membrane for gas separation obtained was obtained by tightening the membrane, it was possible to obtain the effect that both gas permeability and selectivity are extremely excellent.

Claims (1)

[Claims] Selective permsole for gas separation obtained by reacting a polyorganosiloxane with amino-modified side chain ends and a polyorganosiloxane with isocyanate-modified side chain ends on a microporous support membrane to form a thin film. Composite membrane.